This invention relates generally to methods employing biologically active compounds and more particularly to methods employing fungicides.
Fungal infestation of wood structures in the marine environment is damaging in two ways. Directly, fungi cause, in time, deterioration of the wood structure. But more importantly, evidence indicates that fungal infestation is prerequisite for attack by more destructive organisms such as marine borers. The resulting damage to marine wood structures amounts to hundreds of millions of dollars per year.
Fungicides are divided into two general classes which are referred to as protective and eradicant. The former is applied to prevent fungal infection and serves to kill or inhibit the fungal growth as spores settle on the treated material. Eradicant fungicides are used to destroy or eradicate fungi which have already become established and are actively growing. The major differences in characteristics between the two are that the protective fungicide must, in addition, be extremely stable and persistent.
The presistence and stability requirements for protective fungicides on wood in a marine environment are especially high. The water and its motion act to leach out the fungicide or other wood perservatives. This physical phenomena is particularly acute in the warm waters of tropical and subtropical regions. Besides leaching out, some preservatives percolate down the conducting vessels of vertically oriented timbers. These perservatives then collect at the bottom and exude and leach out of the wood. The best example of a preservative having these problems is creosote, which currently has the greatest use. Often creosoted timbers have to be replaced every four or five years on account of deterioration. An additional problem is the resulting pollution to the surrounding water. For example, creosote may be impregnated into pine in amounts as much as 25 lbs/ft.sup.3 ; since creosote is its own solvent, the amount of biologically active material being introduced into the water would be considerable.